Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

Abstract

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single-crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity.

Thermal Route for the Synthesis of Maghemite/Hematite Core/Shell Nanowires

“…After FSD, Lorentzian fits were made using the FSD spectra, and the band assignment was performed taking into account just hematite and maghemite as the iron oxides present in the samples (marked in Figure a). For hematite, we found the allowed Raman modes at 229 cm –1 (A 1g (1)), 245 cm –1 (E g (1)), 295 cm –1 (E g (2)), 300 cm –1 (E g (3)), 410 cm –1 (E g (4)), 496 cm –1 (A 1g (2)), and 612 cm –1 (E g (5)). ,, The vibrational mode at 670 cm –1 (E u ), a longitudinal optical mode, is forbidden in Raman scattering. However, this mode can be activated due to the lattice disorder of hematite .…”

“…Morphology Oxidation state: Raman, Mössbauer and X-ray Absorption spectroscopies Raman spectroscopy is a suitable technique for the identification and discrimination of different oxides. [26][27][28][29] In Figure 3.a we show the average Raman spectra for samples A, B and C obtained from mapping areas on the sample surface together with a Raman spectrum of a sample fully oxidized to hematite (annealed at 500 • for 120 min, see Figure S1.f). In order to improve the spectral resolution and resolve overlapped bands, Fourier Self-Deconvolution (FSD) was performed.…”

“…496 cm −1 (A 1g (2)) and 612 cm −1 (E g (5)). 26,29,33 The vibrational mode at 670 cm −1 (E u ), a longitudinal optical mode, is forbidden in Raman scattering. However, this mode can be activated due to the lattice disorder of hematite.…”

“…For hematite, we found the allowed Raman modes at 229 cm −1 (A 1g (1)), 245 cm −1 (E g (1)), 295 cm −1 (E g (2)), 300 cm −1 (E g (3)), 410 cm −1 (E g (4)), 496 cm −1 (A 1g (2)), and 612 cm −1 (E g (5)). 26,29,33 The vibrational mode at 670 cm −1 (E u ), a longitudinal optical mode, is forbidden in Raman scattering. However, this mode can be activated due to the lattice disorder of hematite.…”

Superstructures on Epitaxial Fe3O4(111) Films: Biphase Formation versus the Degree of Reduction

“…Experimental studies reveal that the conditions for forming the magnetite surface have a strong impact on its structure. This concerns both the surface of epitaxial layers as well as single crystals, for which the surface preparation process (usually ion bombardment) can lead to changes in the surface stoichiometry (oxygen is sputtered easier than iron). − …”